This invention relates generally to gas turbine engines, and more specifically to guide vane assemblies used with gas turbine engines.
Gas turbine engines typically include a compression system, which may consist of a single compressor or multiple compressors rotating at different speeds, for compressing a working fluid, such as air. The compressed air is channeled into a combustor wherein it is mixed with fuel and ignited to generate combustion gases which are channeled to a turbine. The turbine extracts energy from the combustion gasses to power the compressor, as well as to produce useful work to propel an aircraft in flight, or power a load, such as an electrical generator or a ship propeller.
Many known compressors include an outlet guide vane assembly. Outlet guide vanes have airfoil-like cross sections. Known outlet guide vane (OGV) assemblies include a plurality of circumferentially spaced vanes that are spaced substantially uniformly around the compressor outlet. Known OGV assemblies also include a plurality of struts which provide structural support to the compression system and the OGV assemblies.
During operation, blockage created by the struts may induce a non-uniform flow field upstream of the strut and produce a local high pressure area in the vicinity of each strut leading edge which may adversely affect engine operations. Furthermore, within at least some known gas turbine engines, when variable bleed valve (VBV) doors are opened, the non-uniformity of the flow field pressure increases and the affected area expands further upstream. Additional stresses may be induced to a row of rotor blades immediately upstream from the outlet guide vane assemblies.
To facilitate reducing stresses to the rotor assemblies, at least some known engines restrict the operation of the VBV doors. To facilitate maintaining the stresses below predetermined limits, other known engines change the ratio of the vanes to the struts, increase the flow direction spacing between the outlet guide vane and the strut, and/or use a plurality of differently shaped outlet guide vanes.